The Falcon 9 is a two-stage vehicle, so the payload was still on its way into orbit when the first stage came back down. All we really know for certain is that the Zuma satellite, built by Northrop Grumman
, was destined for low-Earth orbit. That's fairly simple as space launches go. Sources who have spoken confidentially to news outlets suggest the satellite failed to decouple from the second stage, leading to it either breaking up in the atmosphere or crashing into the ocean. SpaceX built the second stage, obviously, and Northrop Grumman
built the coupling mechanism for Zuma.